The centrosome proteins Gravin, CEP215, cenexin, pericentrin, primary microcephaly (MCHP2), and PLK1 have all been implicated in regulating the orientation of the mitotic spindle (Chen et al., 2014; Hanafusa et al., 2015; Hehnly et al., 2015; Hung, Hehnly, & Doxsey, 2016; Miyamoto et al., 2017), which can cause downstream consequences such as heart septation defects and microcephaly (Chen et al., 2014; Delaval & Doxsey, 2010; Vertii, Bright, Delaval, Hehnly, & Doxsey, 2015). This evidence concerns the gene PLK1 and microcephaly.